A projector configured to selectively mount, when needed, an optional board (extension board) that is a circuit board having various extension functions to extend functions provided beforehand in the projector is disclosed in, for example, JP2004-264759A. For such a projector, there is known a configuration that includes a mounting unit for selectively mounting an optional unit having various extension function sections.
As the optional unit of this type, for example, there are a wireless LAN (Local Area Network) unit, a RGB (red, green, and blue) signal distribution unit, and an adaptor unit including an extension slot to mount the extension board, each of which includes a plurality of cables electrically connected to substrates located in the projector.
As shown in FIGS. 1 and 2, when optional unit 102 is mounted on mounting unit 104 of the projector, cables of optional unit 102 electrically connected to various extension function sections are electrically connected to substrates 105 and 106 located in the projector.